The present invention relates to a reloadable film canister and particularly to a canister for holding unexposed microfilm used to store blocks of data from camera systems connected to a host computer. Representative prior art for microfilm canisters are disclosed in U.S. Pat. Nos. 4,153,361, 4,987,300, 5,153,625, 5,247,323 and 5,389,992. Typically, the stored microfilm is 105 mm wide and is wound around a core or reel that is inserted into the canister and freely rotates therein. The canister is typically constructed in two segments and has an exit slot for the film. Plush or foam material strips provide a light barrier as the film is pulled out of the canister for use by the camera system or other host machine.
U.S. Pat. No. 4,153,361 discloses a light-tight web cassette for microfilm or the like having supply and take up cartridges mounted thereon. A web detector includes a rotatable, detectable disc external of the cassette. An electrical pulse is generated each time a detectable mark on the rotating disc passes between a light source and photocell, as the two cartridges in the cassette are rotated.
U.S. Pat. No. 4,987,300 describes a system utilizing an optical-mechanical mechanism for a web-roll mounted within a cartridge. A movable flag is rotatably mounted to an underside of the cartridge and is pivoted as the web-roll rotates to interrupt a continuous beam of light of an optical sensing means passing under the cartridge. A light source and photodetecting pair forming the optical sensing means are spaced such that one element of the pair is positioned exterior to the cartridge. A spring-biased member couples the flag with a flange on the web-roll for pivoting of the flag, and a flange lip follower engages spaced notches on the flange lip such that reverse rotation of the web-roll is prevented.
U.S. Pat. Nos. 5,153,625, 5,247,323 and 5,389,992 describe a system in which a field modulating disc is typically located within the light-tight film enclosure. Rotation of this field modulated disc is sensed by an external sensor which generates electrical pulses during the rotation of the reel. These pulses provide information which is accumulated, stored and displayed so that the amount of film removed and, more importantly, the amount of film remaining is known without opening of the canister for visual inspection. Knowledge of the depletion of the film is required to prevent having to splice two rolls of film together when a first roll is expended before all the data are recorded onto the film. It is also desirous to know the film usage to allow a margin for threading of the film into developer equipment, so that data is not lost due to exposure of the film to light.
Heretofore, the above described prior art microfilm canisters offered for sale have not been reloadable by the user. As a result, a significant amount of waste occurs because of the disposal of the canisters after a single use. Moreover, the ultimate user has not been able to use microfilm from a number of film manufacturers, but is instead obligated to discard the canister when each roll of film is depleted and substitute a filled canister purchased from the manufacturer that supplied the system.